U.S. patent application number 11/043324 was filed with the patent office on 2005-08-18 for capacitance sensor.
This patent application is currently assigned to HONDA MOTOR CO., LTD.. Invention is credited to Kikuchi, Taizo, Nakano, Ryuichi, Suda, Hirohide.
Application Number | 20050179445 11/043324 |
Document ID | / |
Family ID | 34697968 |
Filed Date | 2005-08-18 |
United States Patent
Application |
20050179445 |
Kind Code |
A1 |
Nakano, Ryuichi ; et
al. |
August 18, 2005 |
Capacitance sensor
Abstract
A capacitance sensor of the present invention is equipped with a
sensor unit that comprises a pair of detection electrodes, which
are connected to respective reference capacitors, are provided with
being oppositely separated, and can contact each other; and an
insulation member having flexibility by holding at least one
detection electrode. And a capacitance type object detection method
thereof is an object detection method for detecting an object's
nearing: when the object nears, a non-contact sensor detects it
with non contact according to a change of a capacitance; and when
the object makes contact, a contact sensor, which deforms by the
contact of the object, detects it with contact.
Inventors: |
Nakano, Ryuichi; (Wako-shi,
JP) ; Suda, Hirohide; (Wako-shi, JP) ;
Kikuchi, Taizo; (Wako-shi, JP) |
Correspondence
Address: |
MERCHANT & GOULD PC
P.O. BOX 2903
MINNEAPOLIS
MN
55402-0903
US
|
Assignee: |
HONDA MOTOR CO., LTD.
Tokyo
JP
|
Family ID: |
34697968 |
Appl. No.: |
11/043324 |
Filed: |
January 26, 2005 |
Current U.S.
Class: |
324/661 |
Current CPC
Class: |
E05F 15/46 20150115;
E05Y 2800/205 20130101; E05F 15/00 20130101; E05Y 2400/81 20130101;
E05Y 2900/531 20130101; E05F 15/44 20150115; H03K 2217/960765
20130101; E05Y 2800/73 20130101; E05Y 2800/22 20130101; H03K 17/955
20130101; H03K 2217/960705 20130101 |
Class at
Publication: |
324/661 |
International
Class: |
G01R 027/26 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 16, 2004 |
JP |
2004-038980 |
Claims
What is claimed is:
1. A capacitance sensor comprising; a sensor unit; a pair of
detection electrodes that are connected to respective reference
capacitors, are provided with being oppositely separated, and can
contact each other; and an insulation member having flexibility by
holding at least one detection electrode, wherein said sensor unit
includes said pair of the detection electrodes and said insulation
member.
2. A capacitance sensor according to claim 1, wherein said one
detection electrode is held so as to be able to contact the other
detection electrode within closed space formed by said insulation
member.
3. A capacitance sensor according to claim 1 which comprises a
shield electrode that surrounds said pair of detection electrodes
and is arranged in advance in same electric potential as each of
said detection electrodes.
4. A capacitance sensor according to claim 2 which comprises a
shield electrode that surrounds said pair of detection electrodes
and is arranged in advance in same electric potential as each of
said detection electrodes.
5. A capacitance sensor according to claim 3, wherein one detection
electrode held by said sensor unit is provided at a position
corresponding to an opening of said shield electrode.
6. A capacitance sensor according to claim 4, wherein one detection
electrode held by said sensor unit is provided at a position
corresponding to an opening of said shield electrode.
7. A capacitance sensor according to claim 1, wherein a trim unit
for being attached to a door and the like is provided, neighboring
said sensor unit.
8. A capacitance sensor according to claim 2, wherein a trim unit
for being attached to a door and the like is provided, neighboring
said sensor unit.
9. A capacitance sensor according to claim 3, wherein a trim unit
for being attached to a door and the like is provided, neighboring
said sensor unit.
10. A capacitance sensor according to claim 4, wherein a trim unit
for being attached to a door and the like is provided, neighboring
said sensor unit.
11. A capacitance sensor according to claim 5, wherein a trim unit
for being attached to a door and the like is provided, neighboring
said sensor unit.
12. A capacitance sensor according to claim 6, wherein a trim unit
for being attached to a door and the like is provided, neighboring
said sensor unit.
13. A capacitance type object detection method is a method for
detecting an object's nearing, the method comprising the steps of:
detecting the object with non contact by a non-contact sensor
according to a change of a capacitance when the object nears; and
detecting the object with contact by a contact sensor deforming by
the contact of the object when the object makes the contact.
14. A capacitance type object detection method according to claim
13, wherein said non-contact sensor and said contact sensor perform
detection, using a capacitance sensor configured as an integrated
sensor.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a non-contact/contact
integrated type of a capacitance sensor for detecting an object's
such as a human body nearing or contacting a door and the like of a
vehicle.
[0003] 2. Description of the Related Art
[0004] Conventionally, it is known a pinch prevention apparatus
that prevents a hand(s) and a finger(s) from being pinched between
a movable part of a vehicle such as an automatic open/close power
sliding door and power window and a holding part thereof such as a
center pillar and window frame for receiving the movable part (for
example, see paragraphs 0002 to 0026 and FIG. 1 in Japanese Patent
Laid-Open Publication No. 2001-32628). The pinch prevention
apparatus is equipped with a capacitance sensor for detecting a
human body and is designed to stop the movable part according to a
human body detection signal detected by the capacitance sensor or
to move the movable part to an opposite direction.
[0005] Generally, as shown in FIG. 9A, a capacitance sensor is
equipped with a detection electrode El, a grounding electrode E2,
an insulator In pinched between the detection electrode El and the
grounding electrode E2, and a coating member consisting of an
insulation material arranged so as to surround a periphery of the
detection electrodes El and E2 and the insulator In. And the
capacitance sensor is arranged, for example, on an end face at a
side of a movable part facing a holding part.
[0006] In such the capacitance sensor, as shown in FIG. 9B, an
electric charge is supplied to the detection electrode E1 from an
electric charge supply circuit through a pulse generation circuit
and an output amp. That is, because the detection electrode E1 and
the grounding electrode E2 configure a capacitor, an electric
potential V output through the detection amp is expressed in a
following formula (1):
V=Q/(C1+C2), (1)
[0007] where Q represents an electric charge charged in an
capacitance sensor (capacitor), C1 represents a capacitance of the
capacitance sensor itself, and C2 represents a capacitance, stray
capacitance between the capacitance sensor and the ground.
[0008] And if a human body nears the capacitance sensor, the
electric potential V changes according to a capacitance between the
capacitance sensor and the human body. That is, the electric
potential V is expressed in a following formula (2):
V=Q/(C1+C2+C3), (2)
[0009] where Q, C1, and C2 are same as in the formula (1), and C3
represents a capacitance between a human body and a capacitance
sensor.
[0010] Accordingly, the more the human body nears the capacitance
sensor the more the C3 augments, and resultingly, the electric
potential V output through the detection amp becomes smaller and
smaller. In other words, the capacitance sensor is designed to
detect the human body according to the change of such the electric
potential V.
[0011] In this connection, as shown in FIG. 9C, in such the
capacitance sensor there is a case that a droplet W adheres to
peripheries of the detection electrode E1 and the grounding
electrode E2, for example, to the coating member due to rainfall
and the like. Because if the droplet W thus adheres to the coating
member, the capacitance sensor has the grounding electrode E2, a
capacitance thereof increases in an increment of a capacitance Cw
of the droplet W.
[0012] However, if the capacitance Cw of the capacitance sensor
increases, it lowers output of the electric potential V as if a
human body nears the capacitance sensor. Accordingly, the pinch
prevention apparatus using such the capacitance sensor results in
malfunctioning by a disturbance due to the adherence of the droplet
W.
[0013] Consequently, it is strongly requested a novel
non-contact/contact integrated type of a capacitance sensor that
can prevent a malfunction by a disturbance due to the adherence of
a droplet and the like, can perform an accurate detection when an
object such as a human being nears a door and the like of a
vehicle, and can surely detect the object also when it directly
contacts the door and the like.
SUMMARY OF THE INVENTION
[0014] Mechanisms taken to solve the problem described above are
following ones that make it a fundamental inventive idea to design:
to prevent a malfunction by detecting an object such as a human
body through a plurality of detection electrodes provided between
the object and themselves so as not to receive an influenced due to
a disturbance; and to perform sure and accurate detection by making
a structure of the plurality of the electrodes surrounded by a
shield electrode.
[0015] In a first aspect of a capacitance sensor, it comprises a
sensor unit that comprises a pair of detection electrodes, which
are connected to respective reference capacitors, are arranged with
being oppositely separated, and can contact each other; and an
insulation member, which holds at least one detection electrode and
has flexibility.
[0016] In accordance with the first aspect of the capacitance
sensor, it can surely detect an object, which nears at least one
detection electrode of the capacitance sensor provided at a movable
part such as a power sliding door, by an electric potential change
accompanying a capacitance change, and because also when the object
directly contacts a sensor unit having the flexibility, the pair of
the detection electrodes arranged with being separated is provided
to be able to contact each other, and the electric potential change
is detectable, the sensor can surely detect the object in non
contact and contact.
[0017] A second aspect of a capacitance sensor is, in the first
aspect of the sensor, that the one detection electrode is held so
as to be able to contact the other detection electrode within
closed space formed by the insulation member.
[0018] In accordance with the second aspect of the capacitance
sensor, because the pair of detection electrodes is designed to be
held within the closed space formed by the insulation member, it is
easy that the one detection electrode deforms a hollow portion of
the insulation member so as to be able to contact the other
detection electrode and that space of the both electrodes can be
configured as an insulation layer insulated with air, whereby
simplification and weight saving of a structure of the sensor can
be realized.
[0019] In a third aspect of a capacitance sensor, in any of the
first and second aspects, the sensor comprises a shield electrode
that surrounds the pair of detection electrodes and is arranged in
advance in same electric potential as each of the detection
electrodes.
[0020] In accordance with the third aspect of the capacitance
sensor, because a difference between each capacitance of the pair
of the electrodes in an object's nearing or contacting the
electrodes is detected and determined, the shield electrode for
surrounding the pair of the electrodes is provided, and thereby a
disturbance influence of a droplet and the like is prevented, the
sensor can easily obtain a structure that can more accurately
realize erroneous detection prevention. In addition, the sensor can
be suitably used for a difference detection capacitance sensor.
[0021] In a fourth aspect of a capacitance sensor one detection
electrode held by the sensor unit is, in the third aspect of the
sensor, provided at a position corresponding to an opening of the
shield electrode.
[0022] In accordance with the fourth aspect of the capacitance
sensor, because the one detection electrode held by the sensor unit
is designed to be provided at the position corresponding to the
opening of the shield electrode, directivity of electric flux lines
for detection of a nearing object can be heightened. In addition,
sensitivity of the one detection electrode becomes good, and a
disturbance can be prevented as much as possible.
[0023] In a fifth aspect of a capacitance sensor, in any of the
first to fourth aspects, a trim unit for being attached to a door
and the like is provided, neighboring the sensor unit.
[0024] In accordance with the fifth aspect of the capacitance
sensor an attachment structure of the sensor to a door and the like
of a vehicle, where the trim unit (attachment unit) is provided,
can be integrally formed, and an attachment work thereof can be
simplified.
[0025] In a first aspect of a capacitance type object detection
method, it is a method for detecting an object's nearing: when the
object nears, a non-contact sensor detects it with non contact
according to a change of a capacitance; and when the object makes
contact, a contact sensor, which is deformed by the contact of the
object, detects it with contact.
[0026] In accordance with the first aspect of the capacitance type
object detection method, when the object nears to a limit and makes
contact, the object can be surely detected by the contact sensor.
Accordingly, when using such the object detection method for pinch
detection, the pinch can be surely prevented.
[0027] In a second aspect of a capacitance type object detection
method, in the first aspect of the capacitance type object
detection method, the non-contact sensor and the contact sensor
perform detection, using a capacitance sensor configured as an
integrated sensor.
[0028] In accordance with the second aspect of the capacitance type
object detection method, because an electrode structure and the
like can be used for both by using the integrated sensor and
performing detection, and the detection can be performed without
using separate sensors, cost can be reduced in a total system. In
addition, attachment space can be made small.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a perspective view showing a condition when a
capacitance sensor of an embodiment of the present invention is
applied to a pinch prevention apparatus of a power sliding door of
an automobile.
[0030] FIGS. 2A and 2B are section drawings taken along a line A-A
in FIG. 1: FIG. 2A shows an electrode arrangement structure in non
contact; FIG. 2B shows an electrode arrangement structure in
contact.
[0031] FIG. 3 is a schematic drawing of a pinch prevention
apparatus where a capacitance sensor of an embodiment of the
present invention is built in.
[0032] FIG. 4 is a block diagram of the pinch prevention apparatus
of FIG. 3.
[0033] FIG. 5 is a schematic drawing illustrating an operation of
an capacitance sensor of an embodiment of the present
invention.
[0034] FIG. 6 is a flowchart showing control flow of a pinch
prevention apparatus of a non-contact capacitance sensor.
[0035] FIG. 7 is a flowchart showing control flow of a pinch
prevention of a contact/non-contact capacitance sensor.
[0036] FIGS. 8A and 8B are drawings showing experiment results
showing changes of difference values according to a capacitance
sensor: FIG. 8A is a drawing showing an experiment result
representing a change of a difference value in non contact when an
object nears the capacitance sensor; FIG. 8B is a drawing showing
an experiment result representing a change of a difference value
when the object contacts the capacitance sensor
[0037] FIGS. 9A, 9B, and 9C are illustration drawings of a
conventional capacitance sensor.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0038] Here will be described an embodiment of the present
invention in detail, referring to drawings as needed.
[0039] [General Outline]
[0040] In FIG. 1 is schematically shown a capacitance sensor 3 of
the embodiment when applied to a pinch prevention apparatus, which
will be described later, of a power sliding door 1 of an automobile
adopting a power door system. In FIG. 1 the capacitance sensor 3 is
extendedly provided to the power sliding door 1 provided at a side
portion of the automobile along an end at a side of a close side
facing a center pillar 2 of the power sliding door 1 that
opens/closes.
[0041] [Capacitance Sensor]
[0042] As shown in FIG. 1, the capacitance sensor 3 related to the
embodiment is attached across an upper end and lower end of an end
face of the power sliding door 1 facing the center pillar 2 of the
automobile. As shown in FIG. 2A, the capacitance sensor 3 comprises
a sensor unit 4 and a trim part 13 (attachment part) for being
attached to the power sliding door 1. The sensor unit 4 is mainly
configured of a first detection electrode A, a second electrode B
arranged with being oppositely separated from the first detection
electrode A, a shield electrode S for surrounding the first
detection electrode A and the second electrode B, and an insulation
member 5 for coating each of the electrodes A, B, and S.
[0043] The first detection electrode A, second detection electrode
B, and shield electrode S are coated with the insulation member 5,
which makes an external shape of the capacitance sensor 3, and are
arranged so as to extend in a longitudinal direction of the
insulation member 5. In other words, the first detection electrode
A, second detection electrode B, and shield electrode S are
designed to be arranged across the upper end and lower end of the
end face of the power sliding door 1. Meanwhile, as an insulation
material of the insulation member 5, for example, a rubber, an
insulation resin, and the like can be cited.
[0044] As shown in FIG. 2A, the first detection electrode A is
variably provided from a separation position to a contact one for
the second detection electrode B. On the other hand, the second
detection electrode B is fixedly provided within the insulation
member 5. A variable structure of the first detection electrode A
is designed to be realized by a structure of the first detection
electrode A being provided at a reverse side of an obverse portion
5aof the insulation member 5 and arm portions 5b, 5b of the
insulation member 5 being flexibly formed. In addition, the first
detection electrode A and the second detection electrode B are
configured as an integrated sensor by the insulation member 5. The
first detection electrode A, the second detection electrode B, and
the shield electrode S are formed of a strip-form conducting
material of a constant width and length, and the electrode A is
connected to a first reference capacitor CR1 (see FIG. 4) described
later. And as described later, the first detection electrode A is
designed so that constant electric potential is set when the first
reference capacitor CR1 is charged. As a conducting material
composing the first detection electrode A, for example, can be
cited a conducting rubber, a conducting resin, and the like where a
metal powder is contained in a metal or rubber as a filler.
[0045] The second detection electrode B is formed of a strip-form
conducting material having a same width and length as the first
detection electrode A. The second detection electrode B is
connected to a second reference capacitor CR2 (see FIG. 4)
described later, and as described later, is designed so that
constant electric potential is set when the second reference
capacitor CR2 is charged. Meanwhile, in the embodiment, when the
first reference capacitor CR1 and the second reference capacitor
CR2 are charged, the electric potential of the second detection
electrode B is set to become equal to that of the first detection
electrode A. As a conducting material composing the second
detection electrode B, for example, can be cited a conducting
rubber, a conducting resin, and the like where a metal powder is
contained in a metal or rubber as a filler.
[0046] Although the first detection electrode A and the second
detection electrode B show a structure of being arranged so as to
overlap in a detection direction with keeping an opposite distance
in an arrangement mode, the present invention is not limited
thereto, and the structure may be displaced each other in a lateral
direction of the electrodes A and B.
[0047] The shield electrode S is equal to the first detection
electrode A and the second detection electrode B in length and is
formed of a conducting material whose lateral section is
substantially a square form without a left side. As described
later, the shield electrode S is something for preventing a
disturbance for the first detection electrode A and the second
detection electrode B and is arranged so as to be coated at both
sides and a lower side.
[0048] The shield electrode S is connected to act a following
circuit so as to become common electric potential for the first
detection electrode A and the second detection electrode B (see
FIG. 4). As a conducting material composing the shield electrode S,
for example, can be cited a conducting rubber, a conducting resin,
and the like where a metal powder is contained in a metal or rubber
as a filler.
[0049] The first detection electrode A, the second detection
electrode B, and the shield electrode S are configured of
respective electrodes whose polarity is all a same plus pole. The
shield electrode S is arranged so as to surround other three
directions except for an obverse side that becomes the detection
direction of the first detection electrode A, and a bottom portion
Sc of the shield electrode S is arranged in parallel to the first
detection electrode A and the second detection electrode B.
Meanwhile, in the embodiment, although the polarity of the first
detection electrode A and the second detection electrode B is
described as plus, the present invention is not limited thereto,
and one of the electrodes may be made minus.
[0050] As shown in FIG. 2A, the insulation member 5 is formed of a
structure of the sensor unit 4 and the trim unit 13 being
integrally connected. A portion of the sensor unit 4 in the
insulation member 5 is formed like a hollow body having space
inside. In the space an insulator layer is formed, and an air layer
H with an insulation property is formed in the embodiment. An
expansion portion 5c where the first detection electrode A is
arranged is provided inside the insulation member 5 corresponding
to the obverse portion 5a. The second detection electrode B is
arranged with being oppositely separated from the first detection
electrode A on a bottom face of the insulation member 5 opposite to
the expansion portion 5c. It is embedded the shield electrode S
whose section is a square form without one side opening upward
across from the bottom face to leg portions 5d, 5e of the
insulation member 5.
[0051] In the insulation member 5 are flexibly provided arm
portions 5a, 5b for communicating both sides of the expansion
portion 5c with upper portions of side walls Sa, Sb of the shield
electrode S. Nothing but the air layer H intervenes between the
first detection electrode A and the second detection electrode B
arranged inside the insulation member 5. Therefore, if an object
contacts the insulation member 5 and external force acts, the
member 5 is, as shown in FIG. 2B, designed so that the arm portions
5a, 5b flex and the first detection electrode A and the second
detection electrode B can be directly contacted.
[0052] Neighboring the sensor unit 4, the trim unit 13 is
integrally provided with the sensor unit 4, which trim unit 13 is
formed attachable to an edge portion 1a at a close side of the
power sliding door 1. In the trim unit 13 is provided groove 13a
opening in an opposite direction for the detection direction of the
first detection electrode A. The groove 13a is formed to be
attached to the edge portion 1a of the power sliding door 1. On
opposite groove faces within the groove 13a are provided lip-form
stopper nails 13b for pull-out prevention. In the trim unit 13, as
a reinforcement member is embedded a core metal 14 whose section is
a U-shape. One leg of the core metal 14 and the side wall Sb of the
shield electrode S are separated and embedded in the leg portion 5e
of the insulation member 5. Meanwhile, instead of the core metal
14, the shield electrode S may be provided; and in addition,
extending the shield electrode S and integrating it with the core
metal portion, the shield electrode S may be formed.
[0053] The first detection electrode A, the second detection
electrode B, and the shield electrode S provided in the sensor unit
4 shown in FIG. 2A are connected to a detection circuit unit 7 (see
FIG. 4) described later. The first detection electrode A and the
second detection electrode B are something for forming capacitances
between an object 6's (see FIG. 5) nearing the power sliding door 1
(see FIG. 1) and themselves and are coated with the insulation
member 5 whose outer surface has retractility. The insulation
member 5 is preferable to be formed of a resin such as a rubber and
a chemical fiber that have any of the retractility and
flexibility.
[0054] The shield electrode S surrounds three directions except for
a detection direction (extension direction of an opening of the
shield electrode S) of the pair of the first detection electrode A
and the second detection electrode B and is arranged in advance to
become a same electric potential as they are. Accordingly, in a
detection non-operation of a condition of not detecting the object
6 there occurs no electric potential between the first detection
electrode A, the second detection electrode B, and the shield
electrode S. In addition, space between the first detection
electrode A, the second detection electrode B, and the shield
electrode S is insulated by the insulation member 5.
[0055] [Pinch prevention Apparatus]
[0056] In FIG. 3 is shown a pinch prevention apparatus where the
capacitance sensor 3 of the present invention is applied. The pinch
prevention apparatus comprises the capacitance sensor 3, a door
mover 9, an ECU (Electronic Control Unit) 8, and the detection
circuit unit 7. The door mover 9, the ECU 8, and the detection
circuit unit 7 are arranged at a vehicle body side of an
automobile.
[0057] The door mover 9 has a known structure of opening/closing
the power sliding door 1 through an instruction signal output by
the ECU 8 and is configured of an electric motor (not shown), which
rotates normally/reversely or stops in response to the instruction
signal output by the ECU 8, and a push-pull mechanism (not shown)
such as a caterpillar, which receives rotation force of the
electric motor and pushes/pulls the power sliding door 1.
[0058] As shown in FIG. 4, the detection circuit unit 7 comprises
the first reference capacitor CR1, the second reference capacitor
CR2, a charge transfer circuit 7c, a difference detection circuit
7a, and a signal processing circuit 7b. The first reference
capacitor CR1 is connected to the first detection electrode A of
the capacitance sensor 3; and the second reference capacitor CR2 is
similarly connected to the second detection electrode B. In
addition, when power supply is started by a switch operation, the
first reference capacitor CR1 and the second reference capacitor
CR2 are designed to be charged by the charge transfer circuit 7c
and to accumulate reference electric charge. Meanwhile, although
the first reference capacitor CR1 and the second reference
capacitor CR2 may be capacitors of a same capacitance, they may be
capacitors of a different capacitance as needed.
[0059] The reference capacitors CR1 and CR2 in the embodiment are
provided at the detection circuit unit 7 in order to detect and
compare respective capacitance changes of the respective capacitors
occurring between the object 6 and each of the first detection
electrode A and the second detection electrode B and make the
changes a reference when checking electric potential between the
electrodes A and B.
[0060] The charge transfer circuit 7c is designed to be activated
in an ON condition of a door open/close switch (not shown) of the
power sliding door 1 being operated and to charge the first
reference capacitor CR1 and the second reference capacitor CR2 with
the electric charge. In addition, in a complete-close condition of
the power sliding door 1 the charge transfer circuit 7c is designed
to discharge the electric charge charged with the first reference
capacitor CR1 and the second reference capacitor CR2. As the charge
transfer circuit 7c can be adopted one of a known configuration.
The door open/close switch is provided on an inner wall of a
driver's seat door, those of other doors, and the like.
[0061] The difference detection circuit 7a is connected to the
first detection electrode A and the second detection electrode B
and is designed to detect electric potential set for them when the
electric charge is charged in the first reference capacitor CR1 and
the second reference capacitor CR2 and to detect a difference value
between the electric potential of the electrode A and that of the
electrode B. And the difference detection circuit 7a is designed to
output the detected difference value to the signal processing
circuit 7b described next. As the difference detection circuit 7a
can be used, for example, a known differential amplifier
circuit.
[0062] The signal processing circuit 7b is designed to input a
difference detection signal from the difference detection circuit
7a to itself and to compare a difference value based on the
difference detection signal with a difference threshold set in
advance. And the signal processing circuit 7b is designed to
compare the difference value based on the difference detection
signal with any threshold in non-contact or contact and to
determine detection of the object 6 such as a human body.
[0063] FIGS. 8A and 8B are schematic drawings showing experiment
data of non-contact detection and contact detection. In FIG. 8A,
although if the object 6 is located at a sufficiently remote
distance from the capacitance sensor 3, a difference value, which
is output based on a difference detection signal in non contact,
transits in time lapse at a change of an extent of difference value
1 (V) lower than set non-contact threshold 1.7 (V), for example,
when the non-contact threshold is set 1.7 (V) in electric
potential; and if the object 6 nears the capacitance sensor 3, the
output of the difference value drastically augments and the
difference value rises. And if it exceeds the set non-contact
threshold 1.7 (V), the signal processing circuit 7b shown in FIG.
4B outputs a detection signal of the object 6 to the ECU 8.
[0064] On the other hand, in FIG. 8B, if the object 6 directly
contacts the capacitance sensor 3, and accordingly, the first
detection electrode A moves in position and contacts the second
detection electrode B, for example, when a contact threshold is set
0.2 (V) in electric potential, the output of the difference value,
which transits in time lapse at the change of the extent of the
difference value 1 (V), drastically lowers. And if the set contact
threshold becomes lower than the set contact threshold 0.2 (V), the
signal processing circuit 7b outputs a detection signal of the
object 6 to the ECU 8.
[0065] Thus the signal processing circuit 7b is designed to output
the detection signal to the ECU 8 if determining the detection of
the object 6. As the signal processing circuit 7b can be cited one
configured with a CPU (Central Processing Unit) that compares a
memory, where a threshold is stored, with the threshold, referring
to the memory with the difference value based on the difference
detection signal, and outputs the object detection signal to the
ECU 8 when the difference value is within a range of the threshold
set so as to determine the detection of the object 6.
[0066] [Operation of Capacitance Sensor]
[0067] Next will be described an operation of the capacitance
sensor 3, referring to FIGS. 4 and 5. In FIG. 5, for a description,
nothing but the sensor unit 4 is schematically shown, omitting the
trim unit 13. A pair of the first detection electrode A and the
second detection electrode B is arranged with each electrode of
plus polarity. Static capacitors CA, CB are formed between the
conducting object 6 such as a human body and each of the electrodes
A and B. The electrodes A and B are separated each other at a
constant distance (t) within the insulation member 5 through
another insulator such as air and are arranged in a condition of
being surrounded by the shield electrode S. Meanwhile, although an
arrangement relationship of the electrodes A and B is such that
they overlap each other in a detection direction as shown in FIG.
5, they may be displaced and provided so as not to overlap in the
detection direction.
[0068] As shown in FIG. 5, the static capacitor CA is formed with a
distance da between the object 6 and the first detection electrode
A. In addition, the static capacitor CB is formed with a distance
db between the object 6 and the second detection electrode B. The
sensor unit 4 sends respective capacitances to the difference
detection circuit 7a shown in FIG. 4, and the circuit 7a is
designed to output a difference value, which is converted to
electric potential corresponding to the capacitances detected.
[0069] As shown in FIG. 5, for example, because if due to rain and
the like a droplet adheres to a surface and periphery of the
insulation member 5 for coating the first detection electrode A,
the second detection electrode B, and the shield electrode S, side
faces of the electrodes A and B are covered with the shield
electrode S, an influence on the electrodes A and B results in
becoming a small value. For example, because if a surface area of
the first detection electrode A augments in an appearance, and a
change of a capacitance has actually occurred, each of the
electrodes is designed to be same electric potential, the change is
not output as an electric signal. Accordingly, even if a droplet
adheres to a surface of the sensor unit 4, malfunction detection of
the pinch prevention apparatus is prevented from occurring. In
addition, by the shield electrode S, it is reduced a noise that
occurs according to fluctuations of the capacitance due to those of
an external environment (some external environment such as
temperature, humidity, and vibration). Accordingly, it augments a
ratio (S/N ratio) of a signal for a noise that occurs due to the
fluctuations of the external environment, and thus stable detection
sensitivity of the sensor unit 4 can be maintained. Therefore, it
is enabled to set a threshold of the detection circuit unit 7
small, and detection regions of the first detection electrode A and
the second detection electrode B can be enlarged.
[0070] Both shield side walls Sa, Sb (see FIGS. 2A and 2B) of the
shield electrode S function as a directional control mechanism for
limiting directivity of electric flux lines of the first detection
electrode A and the second detection electrode B. The both shield
side walls Sa, Sb are integrally formed with the bottom portion Sc.
Therefore, the electric flux lines extending from surfaces of the
electrodes A and B result in extending in nothing but a direction
not shielded by the both shield side walls Sa, Sb. Accordingly, a
direction of the electric flux lines of the electrodes A and B,
that is, the directivity can be controlled by providing the shield
walls Sa, Sb.
[0071] [Detection Method of Detection Circuit]
[0072] Here will be described a detection operation of the
detection circuit unit 7 where the sensor unit 4 is connected,
referring to FIG. 4. The detection circuit unit 7 shown in FIG. 4
comprises the difference detection circuit 7a and is electrically
connected to the first detection electrode A and the second
detection electrode B. Each connection circuit between the
difference detection circuit 7a and each of the electrodes A and B
is branched within the detection circuit unit 7 and is separately
connected to the reference capacitors CR1, CR2. In the difference
detection circuit 7a a difference occurs in respective capacitance
values that stay in the static capacitors CA, CB at the distances
da, db (see FIG. 5) between the object 6 and each of the first
detection electrode A and the second detection electrode B, wherein
the electrodes A and B have the constant distance t. The difference
detection circuit 7a is designed to detect electric potential
corresponding to a difference of the capacitance values.
[0073] [Detection Method of Difference Value]
[0074] In a difference detection method of a difference value in
accordance with the capacitance sensor 3 of the present invention,
accompanying nearing of the object 6 such as a human body, there
occurs a difference of capacitance values generated between the
object 6 and each of the first detection electrode A and the second
detection electrode B due to a difference of the distances da, db
of the electrodes A and B; and a difference detection method of a
difference value by the capacitance sensor 3 is a method for
converting the difference of the capacitance values to a
corresponding difference value of electric potential, outputting it
to the signal processing circuit 7b, comparing it with a threshold,
and determining detection of any of nearing and contact of the
object 6.
[0075] In other words, as shown in FIG. 1, assuming a condition of
the object 6 such as a human body existing between the power
sliding door 1 and the center pillar 2, a capacitor is formed
between the first detection electrode A and the object 6 as shown
in FIG. 5. From a relationship between a composite value C of a
capacitance consisting of the capacitance (C1+C2+C3) of the formula
(2) accumulated in the capacitor and the electric potential V and
electric charge Q of the first detection electrode A, a following
formula consists:
V=Q/C. (3)
[0076] Here a difference of capacitance values of the first
detection electrode A and the second detection electrode B is
expressed in a following formula:
CA(=.epsilon..times.SA/da)>CB(=.epsilon..times.SB/db), (4)
[0077] where CA and CB are respective capacitances of the first
detection electrode A and the second detection electrode B,
.epsilon. is permittivity of a substance including air existing
between the sensor unit 4 and the object 6, SA and SB are
respective areas of portions of the electrodes A and B assumed to
be opposite to the object 6, and da and db are distances between
the object 6 and the respective electrodes A and B.
[0078] As known from the formulas (3) and (4), because the
capacitance C1 of the first detection electrode A and second
detection electrode B of the sensor unit 4 itself and the
capacitance C2 between the sensor unit 4 and the ground can be
assumed constant, a change of the electric potential may be assumed
to be due to the capacitance C3 between the sensor unit 4 and the
object 6 and to occur due to any of the object 6's such as a human
body existing at and nearing a periphery of the sensor unit 4,
which perform detection. Thus it turns out that if the object 6
such as a human body nears, the electric potential V lowers.
Accordingly, a fundamental principle of the detection method of the
capacitance sensor 3 is a method for converting a change of a
capacitance due to any of the object 6's such as a human body
existing at and nearing the electric potential V to electric
potential and detecting it. Thus because the composite value C of
capacitances augments due to the nearing of the object 6 such as a
human body, non-contact detection is enabled.
[0079] From the formulas (3) and (4), the difference value is
obtained by a difference between electric potential VA and electric
potential VB of the first detection electrode A and the second
detection electrode B, that is, VA-VB. Because the more the object
6 nears the more largely a difference between the distances da, db
is influenced, the difference value VA-VB augments.
[0080] The electric potential difference is detected and used for
detection determination and is converted to the difference value
(electric potential difference value) by the difference detection
circuit 7a.
[0081] The difference value detected by the difference detection
circuit 7a is output to the signal processing circuit 7b. The
difference value output to the signal processing circuit 7b is
compared to two thresholds set by the signal processing circuit 7b
in advance, that is, a non-contact threshold and a contact
threshold. The two thresholds in the signal processing circuit 7b
are set according to a threshold in non contact, for example,
threshold 1.7 (V) set from a peak value when the object 6 such as a
human body nears the first detection electrode A and the second
detection electrode B; and a threshold in contact, for example,
threshold 0.2 (V) when the object 6 directly contacts one
electrode, for example, the first detection electrode A.
[0082] [Operation of Pinch Prevention Apparatus]
[0083] Next will be described a pinch prevention apparatus where
the capacitance sensor 3 of the embodiment is applied, referring to
FIGS. 1 to 4. As shown in FIG. 1, operate a door open/close switch
(not shown) of the power sliding door 1, and move the door to a
storage position of an open condition. In the open condition, if
operating the door open/close switch toward a close side of the
power sliding door 1, the door 1 located at the storage position
start a close progression. By the switch operation, the ECU 8
starts power supply so that an electric motor (not shown) provided
at the door mover 9 normally rotates. Simultaneously, an encoder
(not shown) detects that the electric motor normally rotates and
sends a detection signal thereof to the ECU 8. Simultaneously, the
ECU 8 starts the power supply to the detection circuit unit 7.
Although not shown, to the ECU 8 are connected the detection
circuit unit 7 and the encoder coupled with a drive shaft of the
electric motor of the power sliding door 1.
[0084] Firstly, non-contact detection will be described. When the
power sliding door 1 is being closed by normal rotation drive of
the electric motor, output increases that is formed of a composite
value of capacitances between the object 6 such as a human body and
each of the first detection electrode A and the second detection
electrode B as the object 6 nears the electrodes A and B extendedly
provided at an end of the power sliding door 1. And as shown in
FIG. 8A, when the object 6 nears till just before the electrodes A
and B, output of the detection circuit unit 7 drastically augments
due to the electrodes A and B. The output is detected by the
difference detection circuit 7a of the detection circuit unit 7,
and the detected signal is sent to the signal processing circuit
7b. If an amplitude of the sent electric signal exceeds a threshold
in non contact, for example, the threshold 1.7 (V), the signal
processing circuit 7b outputs a signal to the ECU 8. If the ECU 8
inputs the signal, it determines detection of an abnormal condition
occurrence and issues a stop command for stopping an operation of
the door mover 9. In addition, at the same time the ECU 8 issues a
reverse rotation command for moving the door mover 9 in an opening
direction.
[0085] Meanwhile, because although the detection circuit unit 7
itself has a moving object detection circuit, the first detection
electrode A and the second detection electrode B move together with
a close operation of the power sliding door 1, the unit 7 can also
detect a stationary object existing within a detection region other
than the moving object 6's such as a human body nearing the
detection region.
[0086] If a stop command is issued to the door mover 9 from the ECU
8, it checks the motor normal/reverse rotation detection signal,
and then the door mover 9 instantly stops the electric motor.
Furthermore, the door mover 9 reverses the polarity of the electric
motor and reverses the power sliding door 1. Therefore, the pinch
prevention apparatus can prevent the power sliding door 1 from
pinching the object 6 therein. The embodiment adjusts a detection
region, where a set threshold in non contact is reached, in a range
of about 5 mm to an extent of 50 mm.
[0087] Next will be described direct contact detection. If the
object 6 such as a human body directly contacts the sensor unit 4
of the power sliding door 1 while the power sliding door 1 is
closed, in other words, if the object 6 directly contacts, as shown
in FIG. 2A, the obverse portion 5a of the insulation member 5 of
the sensor unit 4, the arm portions 5b, 5b of the insulation member
5 flex as shown in FIG. 2B, and thereby the first detection
electrode A moves and contacts the second detection electrode B. If
so, as shown in FIG. 8B, the first detection electrode A and the
second detection electrode B become same in electric potential, and
a difference value according to difference capacitances formed
between the object 6 and each of the electrodes A and B drastically
decreases nearly to zero, in other words, not more than a threshold
in contact set the threshold 0.2 (V). If so, the ECU 8 determines
that an abnormal condition occurs, then issues a stop command to
the door mover 9, instantly reverses the polarity of the electric
motor, and thus reverses the power sliding door 1. Therefore, the
pinch prevention apparatus can prevent the power sliding door 1
from pinching the object 6 therein.
[0088] In detection processing thus described, if the signal
processing circuit 7b once sends a detection signal to the ECU 8,
the circuit 7b ignores a new detection signal subsequently sent
from the difference detection circuit 7a until the electric motor
is reversed and stops. In addition, during this time a close
operation of the door open/close switch is ignored by the ECU 8 if
any. The reverse of the electric motor is detected by the encoder
not shown, and a detection signal thereof is sent to the ECU 8. If
the power sliding door 1 finishes opening till a storage position,
the ECU 8 stops the power supply to the electric motor.
[0089] At the same time of the electric motor stopping, the signal
processing circuit 7b becomes to be able to receive a detection
signal sent from the difference detection circuit 7a and to further
perform the close operation of the door open/close switch. In other
words, the signal processing circuit 7b returns to an original
condition. Accordingly, if the close operation of the door
open/close switch is again performed, the stopped electric motor
starts normal rotation. And if the power sliding door 1 again
starts closing, and the ECU 8 detects that the power sliding door 1
reaches the close position, the ECU 8 stops the power supply of the
electric motor.
[0090] In addition, if the ECU 8 detects an abnormal condition, it
can be configured so as to send an actuation signal to a warning
mechanism not shown. In this case, for example, by receiving the
actuation signal, the warning mechanism announces by an electronic
voice through a speaker thereof that the pinch prevention apparatus
is actuated. After the announcement by the electronic voice is
repeated predetermined times, it stops.
[0091] [Flowchart]
[0092] Next will be described an outline of control flow of a pinch
prevention apparatus of the embodiment, referring to FIGS. 6 and 7.
A flowchart shown in FIG. 6 is a description drawing showing an
outline of control flow of a non-contact pinch prevention
apparatus. At time of a start, if power is supplied to the pinch
prevention apparatus, the first reference capacitor CR1 and the
second reference capacitor CR2 are charged, and thus a reference
amount of electric charge is accumulated.
[0093] Firstly, in a step S1 the ECU 8 determines whether or not
the power sliding door 1 is in a moving condition of a close
direction according to whether or not an electric motor is driven
in a normal rotation direction. As a result of the step S1, if the
ECU 8 determines that the electric motor is not driven in the
normal rotation direction, it ends the flow of one cycle. On the
other hand, if it determines that the electric motor is driven in
the normal rotation direction, it advances to processing flow of a
step S2.
[0094] In the step S2 the ECU 8 determines whether or not there
occurs a difference value of electric potential between the first
detection electrode A and the second detection electrode B
corresponding to capacitances from the electrodes A and B of the
capacitance sensor 3. If the ECU 8 determines that there occurs no
difference value of electric potential between the electrodes A and
B, it returns the processing flow to the step S1 and repeats the
processing after the step S1. If the ECU 8 determines that there
occurs the difference value of the electric potential between the
electrodes A and B, it advances to processing flow of a step
S3.
[0095] In the step S3 the signal processing circuit 7b compares an
output difference value with a threshold set in advance, based on
the difference value output from the difference detection circuit
7a corresponding to a capacitance of the capacitance sensor 3 and
thereby determines whether or not there occurs a fear of pinching
the object 6 such as a human body due to its nearing, that is,
presence or absence of pinch. As a result of comparison between the
difference value and the set threshold, if the output difference
value is not more than the threshold, and the ECU 8 determines that
there occurs no fear of the object 6's being pinched, it returns
the processing flow to the step S2 and repeats the processing after
the step S2. On the other hand, if the output difference value
exceeds the set threshold, the ECU 8 determines that there occurs
the fear of the object 6's being pinched, it advances to processing
flow of a step S4.
[0096] In the step S4 the ECU 8 issues a command of
stopping/reversing the drive of the electric motor of the door
mover 9 and thereby instantly stops the motor. At the same time the
ECU 8 reversely changes the polarity of the electric motor and thus
reverses the drive direction of the power sliding door 1 in the
open direction. And if the power sliding door 1 returns to the open
position, the ECU 8 stops the drive of the electric motor. Thus the
ECU 8 ends the processing of one cycle.
[0097] In the step S4, by comparing the difference value and the
threshold set in advance, the ECU 8 determines the presence or
absence of the fear of the object 6's being pinched due to its
nearing the capacitance sensor 3 at the end of the power sliding
door 1 and thereby determines the fear of the object 6 pinch. If
the ECU 8 determines the fear of the object 6 pinch, it is designed
to instantly stop the close progression of the power sliding door 1
and to reverse it by issuing the command of changing the driven
direction of the electric motor. Thus the pinch of the object 6
such as a human body between the center pillar 2 and the power
sliding door 1 can be quickly prevented at non contact timing.
[0098] In each of the steps of the control flow, if the ECU 8 does
not detect abnormality, the power sliding door 1 continues on
driving by the electric motor and completes closing. If the closing
of the power sliding door 1 completes, power supply is shut off,
the electric charge, which is charged into the first reference
capacitor CR1 and the second reference capacitor CR2, is
discharged.
[0099] A flowchart shown in FIG. 7 is a description drawing showing
an idea of control flow of a non-contact/contact pinch prevention
apparatus. A difference of the control flow from that of the
non-contact pinch prevention apparatus shown in FIG. 6 is that in
addition to the non-contact detection in the object 6's such as a
human body nearing the capacitance sensor 3, the former control
flow is enabled to also perform contact detection in the object 6's
directly contacting the capacitance sensor 3. In the control flow
the description till the step 2 will be omitted because it is same
as that of FIG. 6.
[0100] In a step S3' the signal processing circuit 7b determines a
difference value output from the difference detection circuit 7a,
comparing it with a set threshold of the non-contact detection. If
the output difference value from the difference detection circuit
7a is not more than the threshold of the non-contact detection, and
the signal processing circuit 7b determines that there occurs no
pinch of the object 6 such as a human body, it advances the
processing flow to a step S4'. On the other hand, if the output
difference value exceeds the threshold of the non-contact
detection, and the signal processing circuit 7b determines that
there occurs nearing of the object 6, the ECU 8 advances to the
processing of a step S5.
[0101] In the step 4 the signal processing circuit 7b determines
the difference value output from the difference detection circuit
7a, comparing it with a set threshold of the contact detection. If
the difference value output from the difference detection circuit
7a exceeds the threshold of the contact detection, and the signal
processing circuit 7b determines that there occurs no contact of
the object 6 such as a human body, it returns the processing flow
to the step S2 and repeats the processing after the step S2. On the
other hand, if the output difference value is not more than the
threshold of the contact detection, and the signal processing
circuit 7b determines that there occurs contact of the object 6, it
advances to the processing of a step S5.
[0102] In the step S5, same as in the operation of the control flow
of FIG. 6, the ECU 8 issues a command of stopping the drive of the
electric motor and thereby instantly stops the electric motor. At
the same time the ECU 8 changes the polarity of the electric motor
and reverses the drive direction of the power sliding door 1 in an
open direction. And if the power sliding door 1 returns to an open
position, the ECU 8 stops the drive of the electric motor. Thus the
processing of one cycle ends.
[0103] In the steps S3' and S4' the ECU 8 can detect with non
contact/contact any pinch in the object 6's such as a human body
nearing the power sliding door 1 and directly contacting the
capacitance sensor 3 of the door 1 by the first detection electrode
A and the second detection electrode B. Therefore, comparing a
difference value with any set threshold in non contact and contact,
the ECU 8 can determine the presence or absence of the pinch of the
object 6 in the power sliding door 1. Thus because when the ECU 8
determines the pinch, it is designed to issue a command for
changing the drive direction of the electric motor and to instantly
reverse the close progression of the power sliding door 1, the ECU
8 can prevent any pinch of the object 6 such as a human body, which
exists between the center pillar 2 and the power sliding door 1 and
nears the capacitance sensor 3 at the end of the door 1.
[0104] In each of the steps of the control flow, if the ECU 8 does
not detect abnormality, the power sliding door 1 continues on
driving by the electric motor and completes closing. If the closing
of the power sliding door 1 is completed, the power supply is shut
off, and the electric charge charged in the first reference
electrode CR 1 and the second reference electrode CR 2 is
discharged.
[0105] Although in the capacitance sensor 3 of the embodiment thus
described is described an example that the capacitance sensor 3 is
applied to the pinch prevention apparatus between the power sliding
door 1 and center pillar 2 of an automobile, the present invention
is not limited thereto and is applicable to a pinch prevention
apparatus between a movable part and holding part of a vehicle.
* * * * *